With election day looming on 6 November, the two White House rivals campaigned on Tuesday in the key election swing state of Ohio.

Big yellow menace?

Sesame Workshop, the non-profit behind the long-running children's show, said in a statement that it was a nonpartisan organisation.

"We do not endorse candidates or participate in political campaigns," the organisation said.

Analysis

By Mark MardellNorth America editor

The first opinion polls after the big debate make uncomfortable reading for President Obama. But polls are only snapshots. What matters is a trend, not a single figure.

Others wonder whether using Big Bird in an ad is a sign of Democratic desperation. That is rather over the top too: it's not chicken to run an internet advert that gets greater exposure because it's funny and the sort of thing people talk and tweet about.

The Obama campaign has to hit hard. My instinct is that the debate does matter. If you are judging the candidates purely on the debate, purely on who you would want to argue your case if you were on death row, there wasn't much doubt who showed the most conviction and passion. This time next week, the president will have a lot to prove in the second debate.

"We have approved no campaign ads and, as is our general practice, have requested that the ad be taken down."

Obama spokesman Ben LaBolt said the campaign was considering the request.

The US government partially funds PBS and National Public Radio, both targets of conservative politicians.

Mr Obama has used Mr Romney's comments in their first debate to attack the Republican candidate's spending priorities.